Optical recording medium with different wobble characteristics between the user data area and the lead-out area

ABSTRACT

An optical recording medium has a user data area and a lead-out area, wherein the user data area and the lead-out area each has grooves and lands formed thereon. Wobbles are formed on at least one lateral surface of grooves of the user data area and the lead-out area, and configured such that wobble characteristics are made different between the user data area and the lead-out area. Different types of wobbles are formed on the grooves of either the user data area or the lead-out area, thereby preventing an optical pickup that performs recording/reproduction from deviating from the user data area. Also, in a multi-layer optical recording medium, a whole area of a recording layer is configured to have a same condition, thereby preventing deterioration in reproduction and/or recording due to a difference in light power transmittance of another recording layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No.2001-34377, filed Jun. 18, 2001, in the Korean Industrial PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical recording medium, and moreparticularly, to an optical recording medium having wobbles formed on atleast one lateral surface of grooves of a user data area and grooves ofa lead-out area, and configured such that wobble characteristics aremade different between the user data area and the lead-out area.

2. Description of the Related Art

In general, optical recording media are widely employed as informationrecording media for an optical pickup device for recording/reproducinginformation. The optical recording media are classified intoread-only-memory (ROM) compact discs (CDs) and digital versatile discs(DVDs) according to information recording capacity. Further, a DVD disccapable of writing, erasing and reading information can be sub-dividedinto a digital versatile disc-random access memory (DVD-RAM) disc and adigital versatile disc-rewritable (DVD-RW) disc.

In such a DVD-RAM or DVD-RW disc, as shown in FIG. 1, there is a lead-inarea 10 in which read only data, such as disc size, number of tracklayers on a readable plane or illegal copy preventing information, isrecorded, a user data area 20 in which user data can be repeatedly readand/or written, and a lead-out area 30 in which other disc-relatedinformation is recorded.

As indicated by a portion “C” of FIG. 1, there are grooves 23 and lands25 alternatively formed in the user data area 20, so as to performrecording and/or reproducing information marks 27 along a predeterminedtrack. In FIG. 1, reference numeral 40 denotes a reproduction beam. Fromenlarged portions of the lead-in area 10 (“A”) and the lead-out area 30(“B”), it is confirmed that physical pits 15, which is read only data,are formed thereon. Here, the lead-out area 30 performs variousfunctions. For example, the lead-out area 30 guards an optical pickup soas not to deviate from a user data area while the optical pickupperforms recording/reproduction.

In particular, as shown in FIG. 2, in a dual-layer optical recordingmedium having a first recording layer L0 and a second recording layer L1of opposite track paths, the lead-out area 30 allows an optical pickupto keep performing tracking during interlayer jumping from the outermostcircumference of the first layer L0 to the outermost circumference ofthe second layer L1 without deviating from the track paths. The oppositetracks are sequentially addressed from the inner circumference of thefirst recording layer L0 to the outer circumference thereof, and thenfrom the outer circumference of the second recording layer L1 to theinner circumference thereof.

In a dual-layer ROM disc, an area serving as a lead-out area variesaccording to the reproduction method of a second layer. In case of adual-layer ROM disc having opposite track paths, a middle area isseparately provided at each of the outer circumferences of the first andsecond recording layers. However, in case of a rewritable opticalrecording medium, both pits and grooves can be used Therefore, in caseof dual layer rewritable optical recording media, recording power isaffected by the physical geometry of the first recording layer L0 duringrecording of data. In other words, when recording is performed on thesecond recording layer L1, a recording light beam passes through thefirst recording layer L0, resulting in a difference in the transmittancebetween pit portions and groove portions.

Light power was measured for an optical recording medium at a mirrorarea, a pit area, a groove area and a groove area with marks, forsimulation of the light power depending on a difference in thetransmittance according to various conditions of the first recordinglayer L0, as shown in FIGS. 3A through 3D. Here, the number of trackstrapped by laser beam transmitted through a lens was taken intoconsideration.

Tables 1 and 2 list input parameters and items for experimentation. InTable 1, Rc represents the reflectivity of a crystallized portion of arecording layer and Ra represents the reflectivity of an amorphousportion of a recording layer.

TABLE 1 Parameter Condition Wavelength (nm) 400 Numerical Aperture (NA)0.65/0.85 Minimum mark length (μm) 0.275/0.194 Modulation EFM +(Eight-to-Fourteen Modulation-plus) Track pitch (TP) (μm) 0.30, 0.34,0.38 Reflectivity (%) Rc = 25, Ra = 5

TABLE 2 Item Factor Example Dual recording layer Structure of firstrecording Mirror, pits, grooves, layer grooves with marks. High NANumber of tracks trapped  85 for 0.65 of NA by laser beam 160 for 0.85of NA Incident angle of beam 40.5 for 0.65 of NA 58.2 for 0.85 of NA

FIG. 4 is a graph showing the measurement result of light powerdepending on the transmittance for the cases shown in FIGS. 3A, 3B, 3Cand 3D. With reference to FIG. 4, according to the simulation result, adecrease in the light power is smallest in the mirror portion (graphline with solid squares), and the light power gradually decreases morein the order of a pit portion (graph line with solid diamonds), a grooveportion (graph line with solid triangles block) and a groove markportion (graph line with solid circles). Therefore, as shown in FIG. 4,in the case of a dual layer disc, the transmittance varies according tothe physical geometry of the first recording layer L0, which in case ofa rewritable optical recording medium can further affect the recordingpower during recording of data.

SUMMARY OF THE INVENTION

To solve the above problems, it is an object of the present invention toprovide an optical recording medium having a lead-out area configured toprevent a pickup from deviating from a user data area during recordingand/or reproduction of data, without affecting the recording power. Thepresent invention can be applied to optical recording media, whichinclude optical rewritable recording media. In particular, in case ofmulti-layer optical recording media the present invention unifies thephysical geometry of a recording layer as well as provides adiscriminating lead-out area. For example, in a dual layer rewritableoptical recording media, the present invention unifies the physicalgeometry of a first recording layer L0 of the dual layer disc (i.e.,wobbles formed on at least one lateral surface of each groove provide auniform transmittance of an optical light beam passing through arecording layer) as well as newly defines a lead-out area or a middlearea to perform a guard function. A middle area means each outercircumference of the first and second recording layers in oppositetracks. That is, the opposite tracks are sequentially addressed from theinner circumference of the first recording layer L0 to the outercircumference thereof, and then from the outer circumference of thesecond recording layer L1 to the inner circumference thereof.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and, in part, will be obvious fromthe description, or may be learned by practice of the invention.

Accordingly, to achieve the above and other objects of the invention,there is provided an optical recording medium having a user data areaand a lead-out area, wherein the user data area and the lead-out areaeach has grooves and lands formed thereon, wobbles are formed on atleast one lateral surface of each of the grooves, and the wobbles of thelead-out area have different characteristics from those of the user dataarea.

Further, the wobbles of the lead-out area are formed by modulating atleast one feature of frequency, period, amplitude and phase of thewobbles of the user data area.

Further, the wobbles may include addressing information or referencetime information in the form of phase locked loop (PLL).

Further, in addition to the different wobbles in the user data area andthe lead out area, synchronization patterns of signals read from thegrooves of the user data area and the lead-out area are different.

Further, in addition to the different wobbles in the user data area andthe lead-out area, predetermined recording patterns are recorded on theoutermost circumference of the optical recording medium to prevent anoptical pickup from deviating from the user data area during recordingand/or reproduction of data.

In another aspect of the present invention, there is provided an opticalrecording medium having a user data area and a lead-out area, whereinpredetermined recording patterns are recorded on the outermostcircumference of the optical recording medium to prevent an opticalpickup from deviating from the user data area during recording and/orreproduction of data.

Another aspect of the present invention provides an optical recordingmedium having a user data area and a lead-out area, wherein the userdata area and the lead-out area each has grooves and lands formedthereon, and different types of synchronization patterns are used in thelead-out area and the user data area.

Also, two or more recording layers may be provided for multi-layerrecording.

Further, in case of multi-layer recording media, the two or morerecording layers have different recording patterns in their lead-outareas.

Further, in case of multi-layer recording media, the two or morerecording layers have different synchronization patterns in theirlead-out areas.

Further, in the case of multi-layer recording media, the lead-out areahas a width of two or more times the maximum allowance of disceccentricity.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail example embodiments thereof withreference to the attached drawings in which:

FIG. 1 shows an enlarged view illustrating portions A, B and C of aconventional optical recording medium;

FIG. 2 is a partially cross-sectional view illustrating a conventionaloptical recording medium;

FIGS. 3A through 3D illustrate various portions of the conventionaloptical recording medium;

FIG. 4 illustrates the experimental result of light power for variouscases; and

FIG. 5 is an enlarged view illustrating portions A, B and C of anoptical recording medium according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, example embodiments of the present invention will bedescribed in detail with reference to the attached drawings where likereference numerals refer to the like elements throughout. Theembodiments are described below to explain the present invention byreferring to the figures and to more completely explain the presentinvention to anyone skilled in the art. The present invention is notrestricted to the following embodiments, and many variations arepossible within the spirit and scope of the present invention, the scopeof which is defined in the claims and their equivalents.

Referring to FIG. 5, an optical recording medium according to thepresent invention includes a lead-in area 100, a user data area 120 anda lead-out area 130, each area having grooves 123 and lands 125 formedthereon. Wobbles 105 and 135 are formed on at least one lateral surfaceof each of grooves 123 and lands 125 in the user data area 120 and thelead-out area 130. Here, a portion “E” of the user data area 120 and aportion “D” of the lead-out area 130 are enlarged and shown in FIG. 5.Reference numeral 110 denotes a laser beam.

As described above, the lead-out area 130 has a guard function thatprevents an optical pickup (not shown) from deviating from the user dataarea during recording and/or reproduction of data, and in case of adual-layer disc the lead-out area can keep/maintain tracking whileinterlayer jumping from the outermost circumference.

In an optical recording medium according to a first embodiment of thepresent invention, to provide the guard function, wobbles different fromthe wobbles 105 in the user data area 120 are formed in an area beyond apredetermined radius of the optical recording medium (i.e., a lead-outarea). In other words, at least one kind of features including periods,frequencies, amplitudes and phases of the wobbles 105 and 135 aremodulated in the user data area 120 and the lead-out area 130. Thewobbles may include addressing information or reference time informationin the form of phase locked loop (PLL).

For example, the wobbles of the lead-out area 130 can be formed bymodulating at least one feature of frequency, period, amplitude andphase of the wobbles of the user data area 120 as follows. In case ofmodulating the frequencies of the wobbles 105 and 135, the wobble 135 ofthe lead-out area 130 may be formed to have a frequency of n times (n isa real number) the basic frequency of the wobble 105 of the user dataarea 120. The differing wobbles of the user data area 120 and the leadout area 130 unify the physical geometry of the optical recording mediumas well as provide a discriminating lead-out area as a guard. In otherwords, the wobbles formed on at least one lateral surface of each grooveaccording to the present invention provide a uniform transmittance of anoptical light beam passing through a recording layer. For example, tounify the physical geometry of the disc and to serve as a guard, thelead-out area 130 may be configured such that the wobble 135 has afrequency of 2 times that of the user data area 120.

Further, in case of modulating the wobble period T, the wobble 105 ofthe user data area 120 and the wobble 135 of the lead-out area 130 can,for example, have periods 200T and 100T, respectively, so that thelead-out area 130 can be discriminated.

Further, after completion of manufacture of the disc, 00h as patterndata may be recorded in the lead-out area 130. Accordingly, the 00hpattern data is read out by a channel 1 (Ch1) duringrecording/reproduction, and the wobble frequency and/or period can beread out by a channel 2 (Ch2), thereby allowing double discrimination ofthe lead-out area 130.

In an optical medium according to a second embodiment of the presentinvention, when formatting the optical medium, a predetermined recordingpattern can be recorded in the lead-out area 130, thereby discriminatingthe lead-out area 130.

The predetermined recording pattern may be, for example, a recordingpattern used in the user data area 120. That is to say, among recordingpatterns used in the user data area 120, a predetermined recordingpattern, for example, a 00h pattern, can be repeatedly recorded in thelead-out area 130, thereby recognizing the lead-out area 130.

Alternatively, the recording pattern not used in the user data area 120is recorded in the lead-out area 130, thereby recognizing the lead-outarea 130. For example, a 00h pattern is recorded in the user data area120 and an FFh pattern as another pattern is recorded in the lead-outarea 130. Therefore, in this case, the recording patterns recorded onthe lead-out area 130 are different from those used in the user dataarea 120. Here, the 00h and FFh patterns are recording patterns based onthe hexadecimal system.

According to a third embodiment of the present invention, the opticalmedium includes a user data area 120 and a lead-out area 130, eachhaving grooves 123 and lands 125. Different types of synchronizationpatterns (to be abbreviated as “sync patterns” hereinafter) are used inthe user data area 120 and the lead-out area 130. Thus, the lead-outarea 130 is discriminated by recognizing the sync patterns, therebypreventing an optical pickup from deviating from the user data area 120during recording/reproduction. The sync patterns are recorded on thegrooves.

As described above, in an optical recording medium, different types ofwobbles are formed on the grooves of the user data area or the lead-outarea, thereby preventing an optical pickup that performsrecording/reproduction from deviating from the user data area. Further,in an optical recording medium predetermined recording patterns and/ordifferent synchronization patterns can be recorded on the lead-out areaand the user data area alone or in addition to the different typewobbles to provide a guard function preventing deviation of the pickupfrom the user data area. The recording and synchronization patterns inaddition to the wobbles can allow double discrimination of the lead-outarea. Thus, in the present invention, an optical pickup can be preventedfrom deviating from the user data area 120 by discriminating between theuser data area 120 and the lead-out area 130.

The present invention can accommodate a multi-layer optical recordingmedium having two or more recording layers as follows. The multi-layeroptical recording medium includes a user data area 120 and a lead-outarea 130, each having grooves 123 and lands 125. Wobbles 105 and 135 areformed on at least one lateral surface of each of the grooves 123 andthe lands 125. The wobbles 105 and 135 may include addressinginformation or reference time information, e.g., phase locked loop(PLL). To prevent an optical pickup from deviating from the user dataarea 120, the wobbles 105 and 135 formed in the user data area 120 andthe lead-out area 130, respectively, may be modulated into differenttypes of wobbles.

Further, in a multi-layer optical recording medium having two or morerecording layers, different recording patterns are formed on eachlead-out area of the respective recording layers, thereby discriminatingthe respective recording layers. For example, in the case of adual-layer recording medium, a 00h pattern may be recorded on thelead-out area of the first recording layer and an FFh pattern may berecorded on the lead-out area of the second recording layer. By doingso, the recording patterns are read out by a channel 1 (Ch1) and wobblesignals based on wobble modulation are read out by a channel 2 (Ch2),during recording and/or reproducing on/from the optical recordingmedium.

Further, to maintain tracking during interlayer jumping, the width ofthe lead-out area 130 may be determined to be twice or more times themaximum allowance of disc eccentricity. If disc eccentricity accordingto injection in the course of manufacture of a disc is approximately 50μm, the width of the lead-out area 130 is determined to be 100 μm orgreater.

According to another embodiment of the present invention, todiscriminate the respective recording layers in a multi-layer opticalrecording medium having two or more recording layers, different syncpatterns may be used for each recording layer in the lead-out area 130.

As described above, according to the present invention, grooves areformed on a user data area and a lead-out area, and different types ofwobbles are formed on the grooves of either the user data area or thelead-out area, thereby configuring a recording layer of a multi-layerrecording medium to have a same condition and providing a discriminatinglead-out area. The discriminating lead-out area prevents an opticalpickup that performs recording/reproduction from deviating from the userdata area. Also, the configuration of the whole area of a recordinglayer to have the same condition, prevents deterioration in reproductionand/or recording due to a difference in light power transmittance ofanother higher (upper) recording layer. For example, in a dual layeroptical recording medium, the whole area of a first recording layer isconfigured to have a same condition to prevent deterioration inreproduction and/or recording, which requires light power adjustment, ona second layer due to a difference in a transmittance of the firstrecording layer. Therefore, in case of a multi-layer rewritable opticalrecording medium according to the present invention, recording can beperformed on the grooves 123 or on both the grooves 123 and the lands125 and the optical pickup can maintain a uniform light power duringreproduction and/or recording on respective recording layers.

By using such wobbles according to the present invention, a whole areaof a recording layer can be configured to have a same condition,preventing deterioration in reproduction and/or recording due to adifference in the transmittance of a recording layer. Although the wholearea of the recording layer is configured to have the same condition, inthe present invention, an optical pickup can be prevented from deviatingfrom the user data area 120 and the respective recording layers can bediscriminated by using the wobbles according to the present inventionand/or the above described recording and synchronization patterns.

While this invention has been particularly shown and described withreference to example embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. An optical recording medium comprising: a userdata area and a lead-out area, wherein the user data area and thelead-out area each has grooves and lands formed thereon, wobbles areformed on at least one lateral surface of each of the grooves, and thewobbles of the lead-out area have different characteristics from thoseof the user data area.
 2. The optical recording medium according toclaim 1, wherein the wobbles of the lead-out area are formed bymodulating at least one feature of frequency, period, amplitude andphase of the wobbles of the user data area.
 3. The optical recordingmedium according to claim 2, wherein the wobbles of the lead-out areainclude addressing information or reference time information in a formof phase locked loop (PLL).
 4. The optical recording medium according toclaim 2, wherein synchronization patterns of signals read from thegrooves of the user data area and the lead-out area are different. 5.The optical recording medium according to claim 2, wherein predeterminedrecording patterns are recorded on the lead-out area to prevent anoptical pickup from deviating from the user data area during recordingand/or reproduction of data.
 6. The optical recording medium accordingto claim 2, comprising two or more recording layers for multi-layerrecording, each recording layer comprising the user data area and thelead-out area, wherein the user data area and the lead-out area each hasgrooves and lands formed thereon, the wobbles are formed on at least onelateral surface of each groove, and the wobbles of the lead-out areahave different characteristics from those of the user data area.
 7. Theoptical recording medium according to claim 6, wherein the two or morerecording layers have different recording patterns in their lead-outareas.
 8. The optical recording medium according to claim 7, wherein thelead-out area has a width of two or more times a maximum allowance ofdisc eccentricity.
 9. The optical recording medium according to claim 2,wherein recording is performed on the grooves and/or the lands.
 10. Theoptical recording medium according to claim 1, wherein synchronizationpatterns of signals read from the grooves of the user data area and thelead-out area are different.
 11. The optical recording medium accordingto claim 1, wherein predetermined recording patterns are recorded on thelead-out area to prevent an optical pickup from deviating from the userdata area during recording and/or reproduction of data.
 12. The opticalrecording medium according to claim 1, comprising two or more recordinglayers for multi-layer recording, each recording layer comprising theuser data area and the lead-out area, wherein the user data area and thelead-out area each has grooves and lands formed thereon, the wobbles areformed on at least one lateral surface of each groove, and the wobblesof the lead-out area have different characteristics from those of theuser data area.
 13. An optical recording medium having a user data areaand a lead-out area, wherein the user data area and the lead-out areaeach has grooves and lands formed thereon, different types ofsynchronization patterns are used in the lead-out area and the user dataarea.
 14. An optical recording medium, comprising: two or more recordinglayers, each comprising a user data area and a lead-out area; groovesand lands formed on the user data areas and the lead-out areas; andwobbles formed on at least one lateral surface of each groove to providea uniform transmittance of an optical light beam passing through one ofthe recording layers.
 15. The optical recording medium according toclaim 14, wherein the wobbles of the user data area of the one recordinglayer have different characteristics from the wobbles of the lead-outarea of the one recording layer.
 16. The optical recording mediumaccording to claim 15, wherein the wobbles of the lead-out area of theone recording layer are formed by modulating at least one feature offrequency, period, amplitude and phase of the wobbles of the user dataarea of the one recording layer.
 17. The optical recording mediumaccording to claim 16, wherein the lead-out area of the one recordinglayer has a width two or more times a maximum allowance of recordingmedium eccentricity.
 18. The optical recording medium according to claim16, further comprising: predetermined recording patterns recorded on thelead out areas of the recording layers.
 19. The optical recording mediumaccording to claim 16, further comprising: synchronization patterns onthe user data area of the one recording area that differ fromsynchronization patterns on the lead-out area of the one recording area.20. The optical recording medium according to claim 16, whereinrecording is performed on the grooves and/or the lands of the recordinglayers.